How to evenly cover one object with instances of another?
In edit mode, subdivide your mesh a few times, so that the vertices are where you want your jewels to be placed. Then make note of how many vertices your object has (info bar at the top right). Using hair particles, set the number of particles to the number of vertices, make sure even distribution is enabled, and set the emitter to be verts, not faces/volume. That will place a jewel on each vertex, giving you perfectly even distribution, as well as correct rotation.